1. Field of the Invention
The present invention relates in general to a process for producing a thin film transistor suitable to a high integrated static ram (SRAM) or a liquid crystal display, and more particularly to improvements in a leak current and an operating current along with a process for the production of a thin film transistor.
2. Description of the Prior Art
Generally, there occurs a leak current in a thin film transistor (hereinafter "TFT"), which is widely used for operating a liquid crystal display or a SRAM, For example, high temperature treatment has been recently applied to the production of TFT to form an oxide film therein. However, the high temperature treatment causes a leak current to increase in a produced TFT.
In order to reduce the leak current in a TFT, various efforts has been made. In an effort to solve the problem, it is well known to those skilled in the art to increase the hydrogen content of a channel polysilicon layer in the TFT. An increase in the hydrogen content effects a decrease in dangling bond in the channel polysilicon layer, which subsequently brings about reduction of the leak current when switching off the TFT. In addition, the increase in hydrogen content makes it possible to augment an operating current when switching on the TFT. Accordingly, the characteristics of the TFT may be improved owing to the increase in the hydrogen content.
Conventionally, a plasma method utilizing hydrogen gas has been used for increasing the hydrogen content of a channel polysilicon layer in the TFT. Another method is undertaken for the same purpose, as well, comprising depositing PECVD SiN, applying heat treatment to the deposited film and infiltrating hydrogen of the PECVD SiN film into a channel polysilicon layer in the TFT.
However, the problem with these methods is that a sufficient amount of hydrogen does not permeate the channel polysilicon layer.